Opposition supporters in Malawi have been celebrating after a panel of five top judges annulled the results of last May's presidential election.

The vote will now have to be re-run within the next five months. But it is set to take place under different rules.

In essence, the judges argued that Malawians deserve, and should expect, an A- grade election - not perfect, perhaps (who can boast that?) but free of systemic abuse.

Secondly, the court directed Malawi's parliament to consider recalling the current electoral commission to "ensure smooth conduct of fresh elections".

In so doing, they sent a signal that the supposedly neutral bureaucrats in charge of organising such flawed elections should be thrown out. They also implied that a slap on the wrist was not enough, and that Malawi's precious democratic institutions needed to be properly defended.

This was an important blow against a widespread culture of impunity.

Thirdly, the judges said the current first-past-the-post system of picking a new president was unconstitutional. In future, they said, the winner needed to gain more than 50% of the vote, which could mean a second-round run-off.

That could have dramatic political implications for Malawi and is, above all, sure to encourage opposition candidates and parties to enter into strategic coalitions, giving them an unanticipated boost.

Fundamentally, the court ruling weakens the power of incumbency - a power that is often stronger, and more open to abuse, in relatively young democracies.